“We are delighted to welcome these talented actors to the world of Downton," said Gareth Neame, Downton Abbey executive producer and managing director of Carnival Films. "The characters they play are set to bring yet more excitement and intrigue to the show.”

"We look forward to introducing these new characters to our Masterpiece audience. They will make a wonderful addition to the beloved Downton Abbey ensemble," said Rebecca Eaton, executive producer of Masterpiece.

The fourth season, which opened to a series-high 15 million viewers, concludes its run on Masterpiece on Feb. 23.

Downton Abbey is a co-production with Carnival Films and Masterpiece. Neame, Julian Fellowes and Liz Trubridge are executive producers, along with Eaton.